The present invention is generally directed towards an improved mounting for a ROS housing containing the optical components used to direct a modulated scanning beam onto the surface of a photoreceptor, and, more particularly, to a means and method for compensating for scan line (image) skew errors due to photoreceptor-to-ROS misalignment.
Printing systems utilizing a ROS to form images on a photoreceptor surface are well known in the art. Conventionally, the ROS includes a diode or gas laser for generating a coherent beam of radiation; a modulator for modulating the laser output in accordance with an input video image signal; and a multifaceted polygon scanner for scanning the modulated laser beam output line by line, across the surface of the photoreceptor to form the latent image. Also included in the ROS are various optical components to collimate, expand, focus, and align the modulated scanning beams. These optical components are fixedly mounted within a housing frame, which is positioned within a printer machine frame, so that the modulated and shaped scanning beams emerging from a window in the housing are directed in a scan line which is perpendicular to the photoreceptor surface. The lines will be formed in parallel across the surface of the photoreceptor belt. The belt should be aligned so that these parallel lines are formed perpendicular to the direction of belt travel. It is difficult to achieve this perpendicularity, resulting in a condition referred to as "scan line skew", wherein the image effectively takes the form of a parallelogram. This condition will affect the images which are subsequently developed and transferred to output prints, the output prints exhibiting degradation of quality due to the skew effects.